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Circadian Lighting

Circadian Rhythm

Your circadian (latin for “of the day”) rhythm controls many functions of your body. It is entrained by the changing spectral distribution of light – adjusting your body for the environment that it is in. Effectively we are perceiving the movement of the sun across the sky as refraction changes both the colour and spectral distribution.. This is our signal to perform our basic functions and responses
You have probably suffered circadian rhythm disruption – we also call it “Jet Lag”. You feel disoriented, disrupted and tired. Exposing yourself to daylight is one of the best cures. The recent Mars Mission simulations demonstrated extreme circadian rhythm disruption through inappropriate artificial light causing many physical and mental health issues. Following this, NASA will be installing a circadian lighting system on the International Space Station in 2016.
Humans, like other animals, evolved to function in an environment that has a dark/light cycle. In daylight we are active, productive, we eat and we are very alert. In darkness, we sleep, breathe slowly, our heartbeat slows and our core temperature cools. Our modern lives however, require that we use light to see during nature’s dark period, or we live in places where there are less hours of daylight than we evolved to function well in. 
The circadian lighting in this room mimics natural daylight in the day and creates 'biological darkness' at night by changing the colour and spectrum automatically throughout a 24hr period. During the daytime, halcyon will provide the maximum levels of (circadian blue rich) cool white light that has been optimised to stimulate receptors in your eyes (iPRGCs) that will give a strong signal to your body that it is daytime. This can help not only to boost alertness, but also to keep your body in a solid circadian (day/night sleep/wake) cycle. At night time and in the circadian mode, Halcyon will automatically reduce the light levels and change to a very warm glow that has been optimised spectrally to avoid stimulating your iPRGCs. This will allow you to see well as your rods (visual cells in low light) and some of your cones (visual cells in greater light levels) are sensitive in this part of the spectrum, but the non-visual IPRGCs are not very sensitive at all to these redder colours and so your body clock is being told that it is “dark” in biological terms. 

Benefits of Circadian Lighting

  • Improves sleep 1,4
  • Aids stability of body clock 6 - drives natural eating times, reduces night waking 1
  • Faster recovery times 4,5
  • Energising during the day 6
  • Relaxation at evening/night 1,4,6
  • Promotes healthy activity 4,5
  • Increases productivity 7
  • Improves learning 7
  • Improves concentration 7
  • Improves mood & behaviour 6
  • Reduces hyperactivity/ADHD 7
  • Reduces errors and accidents 7
  • Increase in memory 8
  • Faster cognitive processing speed 8
  • Reduces dementia symptoms 2,3
  • Reduces cardiovascular disease 4,5,9
  • Reduces obesity/diabetes 4,5,9
1 Figuieiro and Read, 2005; Roberts, 2008
2 Gehrmann, 2005
3 Torrington , 2006
4 (Roberts, 2000; Vetch et al., 2004; Cutolo M et al., 2005; Heschong and Roberts, 2009).
5 (Wilson, 1972; Stevens et al., 2007; Rea et al., 2008; Erren and Reiter, 2008; Arendt, 2010)
6 (Santillo et al., 2006; Musio and Santillo, 2009; Gaddy et al., Roberts 1995; Czeisler et al., 1995)
7 (Schulte 2010)
8 (Helbig 2013)
9 Fonken et al., 2010

Interesting news and articles on circadian rhythm:

  • 'Design lighting for the body, not just the eyes' - Coverage of a PhotonStar presentation on human centric lighting at Lux Live 2014.
  • Circadian Lighting - Myth or Magic? Video presentation by PhotonStar
  • Researchers find a relationship between sleep cycle, cancer incidence. Researchers have found a protein that regulates your circadian rhythm also protects the body from developing sporadic forms of cancer. 
  • What Sleep Deprivation Does to Your Brain - Infographic
  • A school in Surrey has become the first school in the country to delay morning lessons to accommodate the circadian rhythms of its teenage pupils. Hampton Court House runs lessons from 1.30pm to 7.00pm rather than the standard school hours. Read the article here.
  • Urban light pollution: Why we are all living in permanent 'mini jet lag.' Featuring comment from our circadian advisor, Dr Steven Lockley. Read the article here
  • Are you suffering from social jetlag?
  • Sports coaches seem to be realising the competitive edge that might be gained by working with athletes' circadian rhythm, and that in particular, our light-dark exposure plays an important role. Read more here.
  • Lack of sleep can have role in obesity and diabetes, study says - BBC Report
  • Children's hospital designs sleep app to improve children's sleep - BBC Report